Process and apparatus for removing the outer layer from cereal grains by a wet method

ABSTRACT

A process and apparatus for removing the outer covering from cereal grains by a wet method consisting of subjecting the grains to moisture and to mechanical agitation for mixing the grains and causing them to rub against each other under pressure. The pressure is maintained substantially constant and is uniformly distributed within the mass of the treated grains and in the presence of water equal to between 5 and 15 percent of the dry weight of the grains. The water adheres to the grains by capillary action and penetrates their covers in the course of treatment.

[ 11 3,744,399 July 10, 1973 Szitnkc United States Patent 1 Bonteil thodconsisting of d to mechanical agd causing them to rub ainst each otherunder pressure. The pressure is their cov- Provost........... TarukawaCarkhuff 4/1901 HooIe Wayne illie G. Abercrombie Blanchard and FlynnABSTRACT ocess and apparatus for removing the outer covery constant andis uniformly distributed within the mass of the treated grains and inthe ual to between 5 and 15 percent the grains. The water adheres to3/1932 Bloede 1/1969 Wayne 6 Claims, 1 Drawing Figure Primary Examiner-WAttorney-Woodhams,

A pr ing from cereal grains by a wet me subjecting the grains tomoisture an itation for mixing the grains an 8 maintained substantiallpresence of water eq of the dry weight of the grains by capillary actionand penetrates ers in the course of treatment.

Robert C. Bonteil, CIichy I-Iauts-de-Seine, France Societe DEtude etDExploitation de Procedes pour LIndustrie Alimentaire SEPIAL, Clichy(I-Iauts-de-Seine France Oct. 29, 1970 Appl. No.: 84,997

References Cited UNITED STATES PATENTS 2,217,112 10/1940Hamring.......................... 2,355,810 Loewy Geddes a2 PROCESS ANDAPPARATUS FOR REMOVING THE OUTER LAYER FROM CEREAL GRAINS BY A WETMETHOD [75] Inventor:

[73] Assignee:

[22] Filed:

[30] Foreign Application Priority Data Nov. 24, 1969France...............................

[51] Int.

[58] Field of Search.....................

PROCESS AND APPARATUS FOR REMOVING THE OUTER LAYER FROM CEREAL GRAINS BYA WET METHOD BACKGROUND OF THE INVENTION The present invention relatesin general to a process for removing the outer layer or cover fromcereal grains by a wet method in which the grains are subjected totreatment by moisture, followed by mechanical agitation under pressurewhereby the grains are caused to rub together.

It is known that a process generally similar to the foregoing iscurrently used for removing the exterior, cellulose coverings or layersfrom grains and thereby conserving their ingredients which are rich inproteins. These processes can be applied to wheat, rice, millet sorghum,or to other cereal grains. In the case of wheat, for example, it isdesirable to strip the grain of the epidermis or outer layer of thenucellus, but leave on the grain'the protective layer which surroundsthe albumen.

In the process of the type described in the foregoing paragraph, theoperation of moisturizing the grain consists of making the grains absorba quantity of water equal to around five percent of their dry weight bygently agitating the grains in the water for about two minutes, afterletting the moisture penetrate them for a period of from four tominutes. This way, all the added water penetrates the differentepidermic layers of the grains which has the special effect of softeningthe layer of union separating the epidermis from the epicarp. When thestep of moisturizing the grain is ended, the grains are thus nearly dryon the surface and do not carry away water by capillary attraction sothat they do not adhere to each other. They are then introduced into achamber to be skinned by mechanical treatment.

The chambers generally used for this treatment consist of a verticalcylinder having a coaxial shaft rotatably disposed therein and havingsome stirring vanes thereon. Means are provided for rotating the shaftand, accordingly, the grains within the chamber. The grains areintroduced into the top of the chamber and pushed toward the bottomwhere they are discharged. The grains are thus vertically compressedagainst each other while they move through the chamber.

However, it is established that with existing types of chambers, inwhich the tegmens or outer coverings of the grains are speratedaccording to existing'procedures, the grains are skinned veryimperfectly.

These unsatisfactory results obtained by existing procedures for moistremoval of grain coverings is explained by the fact that two necessaryconditions for obtaining an effective removal of the outer layers of thegrain are not provided: the frictional engagement between the grains isinsufficient and the pressures exerted on the grains are not uniformlydistributed. In effect, due to the fact that the outer surfaces of thegrains are nearly dry and therefore do not adhere to each other whenthey enter into the treatment chamber, the mechanical treatment producesa gentle rubbing of the grains against each other and this rubbingtogether of the grains is not sufficient. The grains are not onlyinsufficiently skinned, but the removal of the tegmens is primarilyproduced by the rubbing of the grains on the walls of the chamber and onthe vanes of the shaft. F urthermore, pressures produced in the chamberare exerted primarily in a vertical direction. Thus, as a practicalmatter, only the horizontal surfaces of the engaging grains are pressedagainst each other. Moreover, the positions of the grains. in thechamber tend to remain insufficiently changed so that the grains are notonly inadequately skinned but also irregularly skinned.

It has been established to the extent necessary that, in existingprocesses, the grains have to be submitted to additional treatment. Forexample, in the case of Algerian hard-grained wheat, it has beenestablished that a single operation and mechanical treatment would notpermit the obtaining of an appreciable proportion of bran. In order toobtain the extraction of bran in the proportion of 3.7 percent byreference to the weight of the dry grains, it has been necessary tosubject the grains to two successive operations of mechanical treatment,similar to that described above, these two supplemental operations beingseparated by a conditioning of two hours during which the moisturepenetrates more deeply into the cellulose layers.

This latter procedure of removing the outer layers of grains is thuslong and complicated, due to the fact that it necessitates separaterecycles, and it does not always produce entirely satisfactory results.

Accordingly, a primary purpose of the present invention is to remedythese disadvantages in existing processes and apparatus for removing theouter layers from cereal grains.

In order to accomplish this end, the process of removing the outerlayers of grains by the wet method according to the invention ischaracterized inthat the grains are subjected to mechanical treatment oragitation under a controlled substantially constant pressure which isuniformly distributed throughout the mass of the treated grains in thepresence of a quantity of water equal to between five and 15 percent ofthe dry weight of the grains, such water adhering by capillary action tothe surface of the grains and penetrating their outer layers in thecourse of the treatment.

Thus, the water retained on the surface of the grains by capillaryaction provides the considerable advantage of materially increasing theforces of friction (especially horizontally) that the grains exert oneach other during the mechanical treatment. The removal of the tegmensis consequently considerably increased by comparison with the prior artprocesses and apparatus.

On the other hand, the water which adheres to the grains by capillaryaction penetrates little by little the exterior layers of the grainsduring the entire duration of the mechanical treatment. Thus, animportant expansion of the grains is achieved at the interior of themixing chamber. That is, the grains are not only compressed verticallyunder a controlled pressure, but their expansion makes them exert directpressures on each other in all directions so that said pressure isuniformly distributed in the mass of the grains in the chamber. Thus,the mass behaves in this respect like a liquid. The forces of removingthe tegmens are applied in a uniform manner on all of the surfaces ofthe grains whereby the removal of the outer layers of the grains is farsuperior to the removal achieved by the prior art procedures for thesame purpose.

At the end of the mechanical treatment, said quantity of water addedexternally to the dry grains has penetrated the coverings of the grainsand the grains thus leave the chamber practically dry again on thesurface.

The peeled grains and the torn tegmens can be sorted out later by anytype of conventional process.

According to the invention, and before the grains are exposed tomechanical treatment, they are soaked in water during a brief periodsufficient for their outer layers to'absorb a small quantity of water,comprising between 2 and 4 percent of the dry weight of the grain.

This small quantity of water saturates the first epidermic layers, sothat the removal of the outer layers can be effectively commenced fromthe moment when the grains are subjected to a mixing action underpressure.

For example, in the case of the hard grained wheat, it has been foundadvantageous to add to the grains a quantity of water representing 1 1percent of the grains dry weight, before subjecting the grains tomechanical agitation, and to leave the grains in contact with the waterduring a time sufficient to absorb about 2.5 percent of the water.

The present invention also concerns an apparatus capable of use incarrying out the process described above, said apparatus including acylindrical chamber in which the grains are mechanically treated bymeans of a rotating shaft having stirring vanes for agitating thegrains, means for delivery of the grains into the chamber, means fordischarging the treated grains, and a pressure control means.

In existing installations of this type, uncontrolled variations in theflow of the grains delivered into the chamber for mechanical treatmentare frequently encountered, as are variations in the discharge of thetreated grains from the chamber. As a result, substantial variations inthe pressure on the grains in the chamber are produced. it follows as adisadvantageous result that, when the pressure is insufficient, removalof the outer layers of the grains is inadequate, and when the pressureis too great, ingredients rich in important nutriments are stripped fromthe nucellus.

Another object of the invention is to remedy the foregoing disadvantageand, in order to accomplish this, the apparatus according to theinvention is characterized by the fact that the pressure control meansincludes a pressure device which can slide on the agitator shaft, inopposition to a force exercised against it by a resilient member, inresponse to variations in the pressure developed within the mass ofgrains in the treatment chamber. The invention is also characterized inthat it includes sensing means for detecting the position of saidpressure device, said sensing means being adapted to effect interruptionin the supply of the grains to the chamber when the pressure devicesmoves past a predetermined position corresponding to a predeterminedpressure in the chamber.

Thus, the means of detecting the position of the pressure means canindicate that the pressure in the chamber is too high and the flow ofgrains into the chamber is thus automatically stopped during the periodof time required to permit the pressure in the chamber to decrease untilit again achieves a desired level.

lt is believed that, as a result of this arrangement, the pressure ofthe grains within the chamber can be automatically maintained at asubstantially constant level slightly lower than a predetermined levelwhich corresponds to a precise position of the pressure means.

In effect, after an interruption in the supply of grains, those grainsalready disposed in the chamber continue to be discharged normally,whereby the pressure of the grains in the chamber is caused to bereduced. The

pressure device is displaced in the opposite direction and, when thepressure in the chamber becomes slightly lower than said predeterminedlevel, the means of detecting the position of said pressure deviceterminates the operation of the mechanism effecting interruption of thesupply; thus, the supply of grains is started again.

It is easy to select, by means of experience, said predetermined levelof the pressure and to consequently regulate the force exerted by theresilient member on the pressure device. Thus, it will be seen that byvirtue of this arrangement the disadvantages of the prior apparatus areeliminated.

Preferably, in accordance with the invention, said pressure device iscomprised of a split disk, including a portion adjacent to the split andsloped with respect to a plane perpendicular to the shaft, and thestirring means are bars extending radially from the shaft to pointsadjacent the sidewall of the cylindrical chamber.

A preferred embodiment of the invention is disclosed by way of examplein the attached drawing in which the single FIGURE representsschematically an apparatus for practicing the process conforming to theinvention.

The apparatus illustrated in the FIGURE includes a silo 1 containing thegrain to be peeled, such as hard grain wheat 2. A conveyor channel 3 ismounted upon an electric vibrator 4, which is connected by theconductors 5 and 6 to a source of electrical energy, and said channel isplaced below the silo l and is arranged in position to collect thegrains which flow from the silo. The discharge end of the channel 3 islocated above the upper open end of a hopper 7 whose lower open endempties through an opening 8a in the sidewall of the inclined cylinder 8near the lower or base end thereof in which an Archimedes screw 9 isrotatably disposed. This screw is mounted on a shaft 10 connected to anelectric motor 11, which is electrically connected to the supplyconductors 5 by the conductors 12. Near its upper end, the inclinedcylinder 8 is connected to a water inlet conduit 13 which is in turnconnected to a source of water, not shown, by means of an electricalgate valve 14. This electrical gate valve is likewise connected to thesupply conductors 5 by means of conductors 15. A conduit for dischargingwater 16 from the cylinder 8 is connected to and communicates with saidcylinder near the lower end thereof.

The cylinder 8 has an opening 8b near its upper end which empties intothe upper end of the mechanical treatment chamber 17 which iscylindrical and mounted on a support 18. Within the chamber 17 there ismounted a coaxial shaft 19 upon which are attached the stirring elements20 which may be comprised of cylindrical bars that extend radially fromthe shaft 19. The central portion of the shaft 19 is surrounded by asleeve 21 which is slideably but nonrotatably connected to the shaft bymeans of a cotter pin 22 which extends through the shaft. The sleeve 21can slide axially of the shaft due to the fact that there are twolengthwise slots 23 in the sleeve into which the extremities of thecotter pin extend.

A split disk 24 is secured to the lower end of the sleeve 21 andincludes a portion of a helical ramp which constitutes a pressuremember. A disk 25 is soldered to the upper end of the sleeve and isengaged by the lower end of the spring 28. The arm 26, serving as adetector of the position of the disk 25, engages a micro-switch 27 whichis connected in series with the electrical supply circuit including thesupply conductors 5. The sleeve 21, the pressure member 24 and the disk25, which are integral, are constantly urged toward the base of thecylinder 17 by the helical spring 28 which surrounds the shaft 19 and isheld under compression between the disk and a locking collar 29 which isadjustably mounted on the shaft 19 near the upper end thereof. Finally,the shaft 19 is coupled at its upper end to the output shaft of anelectrical motor 30 connected to a source of electrical energy in aconventional manner.

The lower end of the shaft 19 is attached to a circular pan 31 which isdisposed directly below the lower end of the chamber 17 and is ofslightly less diameter than the diameter of the chamber so that acalibrated discharge space 32 is provided between the pan 31 and thelower edge of the chamber. Below the pan and said space is placed aconventional separation device connected to a source of air underpressure. Said separation device comprises a channel 33 for receivingthe peeled grains, and it is situated under a collector 34 in which islocated an air discharge head with a back draft 35 connected to a fan 36by a conduit 37, and a discharge channel for bran 38 disposed below theseparation conveyor 39.

OPERATION The apparatus for removing the covers from grain, which hasbeen described above, operates about as follows:

When the chamber 17 for mechanical treatment is empty, prior tooperation thereof, any force exerted against the spring 28 is notproduced by a force applied to the pressure device 24 and, accordingly,the disk 25 is in its lowermost position so that it does not actuate thearm 26 of the micro-switch 27 which therefore remains closed. Theconductors 5 can thus be energized and, when they are, the vibrator 4and the motor 11 are energized and the electric valve gate 14 is opened.This occurs as soon as the electrical system of the apparatus isconnected to a source of energy.

The hard'grain wheat 2 in the silo l flows along the channel 3 away fromthe silo, under the effect of the vibrations created by the vibrator 4,then into the hopper 7 and thereafter enters the opening 8a at the lowerend of the inclined cylinder 8. The motor 11 rotates the Archimedesscrew 9 which, accordingly, advances the grains toward the upper end ofthe cylinder 8 from which they are discharged into the chamber 17through the opening 8b. The electric gate valve 14, being open, permitswater to flow by gravity from the conduit 13 downwardly through thecylinder 8 toward the conduit 16 in a direction opposite to thedirection of movement of the grains being transported 'by the screw. Theflow of water and the grains is so controlled that the water carriedalong by the grains into the mechanical treatment chamber represents 11percent of the dry weight of the grain. The speed of rotation of theArchimedes screw is regulated so that the grains remain for only a briefperiod of time in the cylinder 8. Thus, most of the water carried by thegrains into the treatment chamber is achieved by capillary action, andonly a small proportion, such as between 2.5 percent to 3 percentthereof, enters into the bran through the outer layer.

When the chamber 17 is filled with grains to the level of the pressuremember 24, said pressure member, carried on the shaft 19 by means of thecotter pin 22 and chamber and these grains flow out through thecalibrated space 32. During their movement through the chamber, thegrains are submitted to the forces of friction created by rubbingagainst the wall of the chamber 17 and against the stirring vanes 20.These frictional forces are considerably increased by the fact that thegrains are coated with a film of water creating surface tension betweenthe grains.

To the vertical pressure created by the pressure means 24 is added thepressures created by the grains and exerted uniformly within the chamberupon each other as a result of their substantial expansion. In fact,part of the water, which is carried along by the grains by capillaryaction during entrance of the grains into the mixing chamber, penetrateslittle by little the several epidermic layers of the grains. This alsofacilitates the separation of all the tegmens which surround theprotective layer. The grains are consequently peeled exactly at thedesired level and in a complete and uniform manner, due to the frictionexerted because of the expansion on every surface of each grain. Duringtheir discharge from the chamber, the peeled grains are separated fromthe bran by a blast of air and said peeled grains flow through thecollector 34 into the channel 33 while the bran flows outwardly alongthe conveyor 38 in a normal manner.

By means of the process of the invention, one can thus extract an amountof bran representing 4.95 percent of the dry weight of the grain duringa single movement of the grain through the chamber 17, which is a resultdistinctly superior to the outputs produced by prior processes appliedto the same hard grain wheat.

The pressure upon the grains in the chamber 17 is automaticallymaintained at a substantially constant level in the following way:

When, for example, as a result of a decrease in the discharge of thegrains from the lower end of chamber 17 or as a result of an increase inthe flow of the dry grains being supplied, the pressure of the grains inthe chamber 17 increases, the pressure member 24, the sleeve 21 and thedisk 25 are pushed upwardly toward the upper end of the chamber 17. Thespring 28 is compressed by the upward movement of the disk 25 and thesleeve 21 is permitted to move relative to the extremities of the cotterpin 22 by virtue of the slots 23 in said sleeve.

When the pressure within the chamber 17 reaches a specified level, thedisk 25 reaches a position where it actuates the arm 26 which in turnopens the microswitch 27. The collar 29 is adjusted so that the amountof the pressure within the chamber 17 has reached a predetermined valuebefore the disk 25 actuates the switch 27. While said pressure is equalto'or in excess of said predetermined value, the-vibrator 4 and motor 11are deenergized and the water valve 14 is closed. Thus, the supply ofmoist grains into the chamber 17 is interrupted. The motor 30, however,continues to operate normally so that the treated grains continue,nevertheless, to discharge from the lower end of the chamber 17 and,accordingly, the pressure of the grains within the chamber 17 decreases.As soon as they pressure be comes lower than said predetermined value,the disk 25 is below the point where it causes the arm 26 to open theswitch 27. Thus, the switch 27 is closed whereby theflow of moist grainsinto the chamber 17 again.

It is thus seen that the pressure of the grains in the chamber ismaintained at a substantially constant level which is slightly lowerthan the predetermined pressure value. An important factor in themechanical treatment of the grains is thus automatically controlledwhereby the high quality of the treatment of the grains is additionallyassured. It is to be noted that the regulation of the pressure withinthe chamber 17 does not disturb the flow of treated grains dischargedinto the channel 33 since such discharge in the chamber is neverinterrupted.

In one particular embodiment of the invention, the inflow of grains intothe chamber 17 is interrupted when the pressure on the grains in saidchamber reaches approximately 150 grams per square centimeter.

Although a particular preferred embodiment of the invention has beendisclosed in detail for illustrative purposes, it will be recognizedthat variations or modifications of the disclosed apparatus, includingthe rearrangement of parts, lie within the scope of the presentinvention.

The embodiments of the invention in which an exclusive property ofprivilege is claimed are defined as follows:

1. A process for removing the outer layer from cereal grains, comprisingthe steps of:

subjecting said grains to a quantity of water for a brief period of timeduring which said grains absorb a small amount of said water and alarger amount of said water clings to the outer surface of said grains;

moving said grains and said water into the upper end of a chamber forcreating a mass of grains within said chamber;

maintaining the mass of grains in said chamber in a moist condition, thetotal amount of water absorbed by and clinging to said grains being inthe range of from to percent of the dry weight of said grains;

applying a substantially constant compressive pressure to the mass ofmoist grains within said chamber so that a substantially uniformcompressive pressure is applied on the grains throughout said mass;

agitating said mass of moist grains within said chamber by mechanicalmeans for removing the outer layer from said grains;

discharging said grains from the lower end of said chamber; and

interrupting the movement of said grains and said water into saidchamber whenever the pressure within said mass exceeds a predeterminedlevel.

2. A process according to claim 1, comprising the step of subjectingsaid grains to said quantity of water for a sufficient period of time tocause said grains to absorb an amount of water equal to between 2 and 4percent of their dry weight before they enter said chamber, andsubjecting said grains to said quantity of water for a sufficient periodof time to cause the total amount of water absorbed by and clinging tosaid grains to be begins equal to approximately I l percent of the dryweight-of said grains.

3. An apparatus for removing the tegmens from cereal grains, comprising:

means defining an upright agitation chamber for receiving moist grains,said chamber having an inlet opening at the upper end thereof and adischarge opening at the lower end thereof;

an inclined conveyor having an upper end discharging into the upper endof said chamber;

receiver means near the lower end of said conveyor adapted to beconnected to a source of grains for guiding said grains onto theconveyor;

a source of water and conduit means for guiding said water intoengagement with said grains on said conveyor, whereby a certain amountof said water is absorbed by said grains and another. amount clings tothe outer surfaces of said grains;

agitation means within said chamber for moving the grains therein;

pressure means engageable with said grains within said chamber forapplying to said grains a substantially constant and uniform compressivepressure while simultaneously permitting a varying supply of grain intosaid chamber;

drive means for operating said conveyor and valve means controlling theflow of said water; and

sensing means responsive to said pressure means for deactivating saiddrive means and closing said valve means when said pressure in saidchamber exceeds a predetermined amount and for activating said drivemeans and opening said valve means when said pressure in said chamberfalls below said predetermined amount.

4. An apparatus according to claim 3, wherein said pressure meansincludes a split disc positioned within said chamber and disposed forengaging the mass of grains in said chamber for compressing same, saidpressure means including means biasing said split disc into engagementwith said mass of grains for urging same toward said discharge opening,said split disc including a helically sloped portion disposed directlyadjacent the split, the sloped portion extending at an angle relative toa plane substantially perpendicular to the longitudinally extendingdirection of said chamber.

5. An apparatus according to claim 4, wherein said agitation meansincudes a rotatable agitator member disposed within said chamber, saidagitator member having an elongated rotatable shaft disposedsubstantially centrally within said chamber and extending 1ongitudinallythereof; and

said split disc being disposed substantially in surrounding relationshipto said shaft adjacent the upper end of said chamber, and resilientmeans coacting with said disc for resiliently urging same downwardlyinto engagement with the upper portion of the mass of grains containedwithin said chamber.

6. An apparatus according to claim 5, further including means fornonrotatably connecting said split disc to said shaft while permittingsaid disc to slideably move axially relative to said shaft.

1. A process for removing the outer layer from cereal grains, comprisingthe steps of: subjecting said grains to a quantity of water for a briefperiod of time during which said grains absorb a small amount of saidwater and a larger amount of said water clings to the outer surface ofsaid grains; moving said grains and said water into the upper end of achamber for creating a mass of grains within said chamber; maintainingthe mass of grains in said chambeR in a moist condition, the totalamount of water absorbed by and clinging to said grains being in therange of from 5 to 15 percent of the dry weight of said grains; applyinga substantially constant compressive pressure to the mass of moistgrains within said chamber so that a substantially uniform compressivepressure is applied on the grains throughout said mass; agitating saidmass of moist grains within said chamber by mechanical means forremoving the outer layer from said grains; discharging said grains fromthe lower end of said chamber; and interrupting the movement of saidgrains and said water into said chamber whenever the pressure withinsaid mass exceeds a predetermined level.
 2. A process according to claim1, comprising the step of subjecting said grains to said quantity ofwater for a sufficient period of time to cause said grains to absorb anamount of water equal to between 2 and 4 percent of their dry weightbefore they enter said chamber, and subjecting said grains to saidquantity of water for a sufficient period of time to cause the totalamount of water absorbed by and clinging to said grains to be equal toapproximately 11 percent of the dry weight of said grains.
 3. Anapparatus for removing the tegmens from cereal grains, comprising: meansdefining an upright agitation chamber for receiving moist grains, saidchamber having an inlet opening at the upper end thereof and a dischargeopening at the lower end thereof; an inclined conveyor having an upperend discharging into the upper end of said chamber; receiver means nearthe lower end of said conveyor adapted to be connected to a source ofgrains for guiding said grains onto the conveyor; a source of water andconduit means for guiding said water into engagement with said grains onsaid conveyor, whereby a certain amount of said water is absorbed bysaid grains and another amount clings to the outer surfaces of saidgrains; agitation means within said chamber for moving the grainstherein; pressure means engageable with said grains within said chamberfor applying to said grains a substantially constant and uniformcompressive pressure while simultaneously permitting a varying supply ofgrain into said chamber; drive means for operating said conveyor andvalve means controlling the flow of said water; and sensing meansresponsive to said pressure means for deactivating said drive means andclosing said valve means when said pressure in said chamber exceeds apredetermined amount and for activating said drive means and openingsaid valve means when said pressure in said chamber falls below saidpredetermined amount.
 4. An apparatus according to claim 3, wherein saidpressure means includes a split disc positioned within said chamber anddisposed for engaging the mass of grains in said chamber for compressingsame, said pressure means including means biasing said split disc intoengagement with said mass of grains for urging same toward saiddischarge opening, said split disc including a helically sloped portiondisposed directly adjacent the split, the sloped portion extending at anangle relative to a plane substantially perpendicular to thelongitudinally extending direction of said chamber.
 5. An apparatusaccording to claim 4, wherein said agitation means incudes a rotatableagitator member disposed within said chamber, said agitator memberhaving an elongated rotatable shaft disposed substantially centrallywithin said chamber and extending longitudinally thereof; and said splitdisc being disposed substantially in surrounding relationship to saidshaft adjacent the upper end of said chamber, and resilient meanscoacting with said disc for resiliently urging same downwardly intoengagement with the upper portion of the mass of grains contained withinsaid chamber.
 6. An apparatus according to claim 5, further includingmeans for nonrotatably connecting said split disc to said shaft whiLepermitting said disc to slideably move axially relative to said shaft.